Measurement and reconstruction of the golf launching scene in 3D

ABSTRACT

A golf launching monitoring arrangement allows equipment to be placed at a position behind the player (i.e., behind the golf ball), to measure both club and ball movement. A 3D scan of the club head before the play serves two purposes: 1) 3D registration that enables accurate measurement of the club head position and orientation for the camera system measuring the club movement from the back; 2) for reconstruction of the launching scene. With a 3D model of the club head, a simple 3D model of the golf ball and accurate measurement of their movement during the play, a full 3D golf launching scene can be reconstructed authentically. With this reconstruction, the movement of both the club head and the resulting ball movement can be replayed at any viewing angle, with any frame rate and at whatever resolution for the players or the coaches to view and analyze.

BACKGROUND

There are two main approaches for existing golf launching monitors:radar based or vision (camera) based. Compared to radar solutions, thevision solution is much cheaper and works well both indoor and outdoor;vision-based solutions can measure certain parameters, e.g. the lieangle, that the radar-based monitors cannot. They can also provide moreaccurate results for some key parameters, such as total spin and spinaxis. Described herein is a vision-based solution for both club and ballmeasurement.

Vision-based methods for ball measurement are known; and there are alsosystems available for the measurement of both club and ball. However,existing solutions require the measuring system to be placed in a sideposition in relation to the player and the ball, and additional stickersneed to be placed on the club face.

The side-ways placement encounters various problems: 1) differenthardware setups/settings are needed for right-handed and left-handedplayers; 2) positioning of hardware within the view of the player may bea distraction to the player; and 3) proximity of the hardware may resultin damage to the hardware caused by the swing of the club.

Placement of additional stickers on the club face makes the visionsolution more robust, but entails additional cost and work for the usersand affects the appearance of the club, which is not desirable for theusers. Moreover, stickers placed on the club face are susceptible towear.

To fully understand the golf launching results, high speed cameras, e.g.with 1000 fps, have been used to capture the movement of club and ballnear the impact instance. This helps coaches and players to betterrelate the club movement and the impact on the ball, which can lead tothe improvements in performance. However, this solution requiresexpensive hardware, and the video can be only view from one specificangle, with fixed resolution.

There are two categories of measurement in golf launch monitoring: theball parameters and the club parameters. The present description ismainly related to the measurement of the club parameters, as themeasurement of ball parameters has been covered in previous disclosuressuch as U.S. Pat. No. 9,171,211 B2.

The measurement of full 3D postures (position and orientation) of theclub head during hitting is a challenging task for camera-based systemsbecause of the lack of consistent distinguishing features across so manydifferent kinds of club heads. To handle this problem, one known system(described in U.S. Pat. No. 8,951,138 B2, for example), puts the cameraat the side of the player and require the player to put special stickerson the club face for detection and measurement. This approach can betroublesome to the player, and changes appearance of the club head.

BRIEF DESCRIPTION OF THE DRAWING

The present invention may be understood from the following descriptionin conjunction with the appended drawing figures. In the drawing:

FIG. 1 is a block diagram of a golf launch monitoring system.

FIG. 2 is a block diagram of the measuring device of FIG. 1.

FIG. 3 is a flow diagram of a measurement procedure that may be used inthe system of FIG. 1.

FIG. 4 is a diagram of a known club head, identifying parts thereof.

FIG. 5 is a stereo image pair (background removed) showing a driver andball before impact.

FIG. 6 is an illustration of a marker exhibiting a phase shift patternof grayscale changes, with a sine wave superimposed thereon.

FIG. 7A is a first image of a stereo image pair of a marker on theshaft.

FIG. 7B is a second image of a stereo image pair of a marker on theshaft.

FIG. 8A is a first image of an image pair showing observed phase shiftpatterns for left and right images.

FIG. 8B is a second image of an image pair showing observed phase shiftpatterns for left and right images.

FIG. 9 is an image illustrating Lambertian reflectance of a cylindricalobject in accordance with a theoretical model.

FIG. 10 is an image of a marker provided with a reference band to enablereflectance variation removal.

FIG. 11A is an image of one suitable phase shift pattern.

FIG. 11B is a diagram of an intensity profile corresponding to the phaseshift pattern of FIG. 11A.

FIG. 12 is an image of phase shift pattern modulated in two dimensions.

FIG. 13 is an image of a stacked 2D modulated phase pattern for betterrobustness and accuracy.

FIG. 14 is a diagram illustrating estimation of impact from the golfball movement.

FIG. 15 is a diagram showing face angle variation on woods depending onclub face location. Variation can occur both horizontally and verticallyfor both woods and drivers.

FIG. 16 is a block diagram illustrating 3D reconstruction of the fulllaunching scene.

FIG. 17 is a block diagram of another embodiment of the measuring deviceof FIG. 1.

FIG. 18 is a flow diagram showing additional club scanning details.

FIG. 19 is a flow diagram showing additional details of club and ballmeasurement.

FIG. 20 is a flow diagram showing additional details of trajectorymeasurement.

DETAILED DESCRIPTION Summary

A vision-based, rear-placement golf launch monitoring system is providedwithout any requirement of additional markers, providing a moredesirable solution for golfers. This system can measure the club headmovement and orientation from the back of the player without anyrequirement of additional markers/stickers. In other embodiments, amarker may be placed on the club shaft in order to simplify hardwarerequirements.

With a full 3D model of the club head, a simple model of the ball andaccurate measurement of their respective movements, a 3D model of thelaunching scene can be fully reconstructed in high fidelity. Usingexisting computer graphics method, this 3D model can re-generategraphics of the launching scene to be replayed at any viewing angle,with any frame rate and with any resolution. It allows the user tointeract with the graphics and may use known hardware components.

By placing the measurement device behind the player (i.e., behind thegolf ball), the system can be used for both left-handed and right-handedplayers without any discrimination. It can be located at a safe distanceaway from the action zone, and it will not cause any distraction to theplayer.

By means of 3D scanning of the club head and consequent measurement ofits 3D movement, the full sequence of the club and ball movement can beaccurately measured and fully reconstructed in 3D without therequirement of putting special stickers on the club face. This 3Dreconstruction then allows the user to view the action from anyperspective, with whatever resolution and frame rate. For example, aslow motion effect which is currently only possible with a high-end1000FPS camera can be achieved. The 3D reconstruction also allows theuser to interact with the re-play.

Scanning the club head in 3D enables the roll and bulge of the club faceof woods and drivers to be compensated.

DESCRIPTION

Referring to FIG. 1, a block diagram is shown of a golf launchmonitoring system, showing the system setup. A measurement device 110 ispositioned on the floor or ground behind the golfer 131 (i.e., behindthe golf ball 133), who uses a golf club 135 to strike the golf ball.Processing of data can be further done through a cloud service. Aviewing device 120 is provided for the user to visualize the measurementresults.

FIG. 2 illustrates a block diagram of the measuring device 110 inaccordance with one embodiment. In one embodiment, the measurementdevice may include four cameras. Two higher-speed, lower resolutioncameras 101A, 101B form a stereo system for measurement of the club andball movement during the swing, and two slower-speed, higher-resolutioncameras 103A, 103B form another stereo system for measurement of theball trajectory. In this embodiment, the system also includes anadditional lighting system 104 to ensure properly lit images, astructured lighting module 105 for 3D scanning of the club head, a radarsystem 106 for providing timing and sequencing of image capture by thecameras, a computing sub-system 107 that performs some real-timeprocessing, and a wireless communication sub-system 109 to send data tothe viewing device.

The measurement of the launching scene is mainly based on the first pairof cameras 101A, 101B, which is supported by a lighting system 104 and astructured lighting module 105 for 3D scanning of the club head. Thesecond pair of cameras 103A, 103B may be used for measurement of thegolf ball trajectory, details of which will not be described herein. Theradar unit 106 may used to detect the starting of the player's swing totrigger the working of the cameras. Precise timing and synchronizationof the cameras may be done by the computing and controlling system 107,which may be a real-time computing and controlling system, realized inFPGA form, for example. The wireless communication system 109 is used totransmit out the measurement results to the viewing device.

The present disclosure is mainly focused on the use of the first pair ofcameras for measuring the club and ball movement right before and afterthe impact. Using a pair of synchronized cameras (e.g., cameras 101A,101B), together with the club head 3D scanning data, the club head andball movement may be reconstructed in 3D space with very high accuracy.The reconstruction may use stereo vision techniques.

FIG. 3 shows the sequence 10 of the measurement during a golf play usingthe system, in accordance with one embodiment. The first step is beforethe player starts playing with a club that is not registered with thesystem, he/she is instructed to put the club head before the measuringdevice, whereupon the system works in a 3D scanning mode to scan theclub head (301). Using structure lighting and two cameras, when the userturns the club head around, a series of stereo images pairs with knownlighting patterns are captured. Using existing computer visiontechniques, a 3D model of the club head can be re-constructed withsub-millimeter level accuracy.

Also before the play, the system will search for the golf ball in alaunching area and do 3D measurement of the static golf ball (303). Thisinformation will be used for accurate modelling of the ball and accuratecalculation of impact time.

Then the player is ready to play with the registered club. During eachswing, the measuring device enters measurement mode and automaticallycaptures the images and performs measurement on both the club and theball (307, 309).

Further details of the steps of FIG. 3 are shown in FIGS. 18, 19 and 20.

Referring to FIG. 18, when the system is ready for club head scanning,the user is instructed through a user interface (UI) on the viewingdevice, which indicates to the user where to position the club head forscanning (1801). The cameras 101A, 101B detect the club head, triggeringsynchronized structured lighting and video recording for an interval,e.g., 3 second (1803). The video is successfully recorded and the systemindicates completion through the viewing device, and (optionally) bylighting up an LED.

Referring to FIG. 19, where the system is ready for golf launching, itinstructs the user through UI of the viewing device and indicates alocating to put the golf ball, e.g., using a visible laser point (1901).The cameras 101A, 101B detect the presence of the golf ball and startradar operation for club speed measurement (1903). The radar detects areversal of club head speed and triggers the cameras 101A, 101B to runin a high-FPS mode for continuous image capture to capture the club headin the field of view (FOV) (1905). When the club head is detected in thecamera FOV, the system enters “club measurement” mode (1907). Thecameras 101A, 101B then capture some number of image pairs of the clubhead with timing being based on club head speed estimated by the radarsystem. Thereafter, the cameras 101A, 101B start to run in high-FPS modeagain to detect re-appearance of the golf ball in the FOV followingimpact (1909). When the golf ball has been detected in the FOV, thesystem enters “ball measurement” mode (1910). The cameras 101A, 101Bcapture some number of pairs of images (e.g., 10) of the golf ball withtiming being based on club head speed estimated by the radar system.

Referring to FIG. 20, after “ball measurement is finished,” a“trajectory cameras” mode is triggered (2001). The trajectory cameras103A, 103B capture images of the golf ball trajectory in a low-FPS(e.g., 30 FPS) mode with high resolution for a timer period (e.g., threeseconds) (2003). The system finishes the measurement and providesfeedback to the user through UI and the viewing device and (optionally)by lighting up of a status LED (2005).

For the measurement of the ball movement, further details of suitablemethods are described in previous patents of the present assignee,including U.S. Pat. No. 9,171,211 B2, incorporated herein by reference.The measurement of the ball trajectory may likewise incorporate knowntechniques. The present description mainly focuses on methods formeasurement of the club movement.

The measurement of the attack angle, club path and speed may beperformed by measuring the 3D position of the center of gravity (COG) ofthe club head, which is very near to the center of the pixels of theclub head in the image domain. The speed measurement accuracy can befurther improved with the measurement from the radar. The 3D positionfor each pair of images at every time sample may be determined bymeasuring the difference between the center of the club head pixels.Traditional stereo vision method can be applied to deliversub-millimeter accuracy.

As the system is observing the club head from the back, the 3Dorientation of the club face needs to be determined by a 3D registrationprocedure. With the 3D data of the club head from the previous3D-scanning process, the club face position and orientation at each andevery frame can be accurately determined with a 3D registration process.

FIG. 4 illustrates parts of a known club head, including ferrule 401,hosel 402, crown 403, toe 405, sole 406, face 407 and heel 409. Thereare multiple approaches for the 3D registration process, two examples ofwhich will be described. The first approach is based on two sources ofdata: 1) measurement of a 3D line segment between Hosel and Ferrule onthe club shaft, which does not bend during the swing, using stereovision techniques; and 2) the location of features, such as thesilhouettes, observed by the two cameras. Both of these can be measuredaccurately using the images captured by stereo system as shown in FIG.5. With a 3D model of the club head generated from the 3D scanning,software techniques are used to find a 3D orientation (together with the3D position) of the 3D model that best matches with the two observationsat any time instance. The RMS error of this estimation method is lessthan one degree in 3D space. With this registration done, the lie angleis also determined with accuracy of less than one degree.

The second approach requires a marker to be attached to the club shaft,near the tip region. Compared to the existing system which requiresmultiple stickers to be put on different locations on the club face, themarker design and placement is much easier, causes less appearanceissues with the club and will not wear out as it does not contact theball at all. At the same time, the use of a special designed markerenables a single camera solution. FIG. 6 is an illustration of a markerexhibiting a phase shift pattern of grayscale changes, with a sine wavesuperimposed thereon. A design pattern of the marker helps to determinethe rotation angle around the shaft axis very accurately. The pattern(named “phase shift”) may be used to enable image processing to measurethe rotation angle with 0.5 degrees accuracy when observed at a distanceof about 2 meters. With the shaft 3D position accurately measured withthe stereo camera system, together accurate measurement of the rotationangle using this pattern, the face orientation may be determined with 1degree accuracy using the 3D registration process.

FIG. 7A and FIG. 7B show a stereo image pair with the marker attached toa club. The marker region can be first detected and rectified usingimage processing techniques such as edge detection, feature detection,rotation estimation and perspective correction, which give rise to therectified observations of the marker as shown in FIG. 8A and FIG. 8B.These observations may be further processed to remove the reflectancevariation caused by the cylindrical shape of the shaft, as illustratedby the theoretic model shown in FIG. 9.

In practice, the reflectance variation can be measured with a referenceband of uniform intensity value as shown in FIG. 10. The upper part 1001of the image is the uniform white color band used as reference. Theobserved variance in the grayscale value in this band can be used tocorrect the reflectance variation in the observed phase shift pattern1003. This reference-based method can be more accurate than using thetheoretical model, as the latter does not include factors such aswavelength of the light source, the reflectance coefficient of themarker, the camera response function etc., which are all included in thedirect measurement.

With the reflectance variation compensated, the observed markers may becorrelated with the designed phase pattern using a FFT (Fast FourierTransformation) registration method, which can give the accuracy of onetenth of a pixel; in contrast, conventional edge detection can only giveup to half a pixel accuracy in such lighting conditions. This shift inpixels is finally converted to the rotation angle around the center axisof the shaft with known marker size and optics of the imaging system.The correspondence between this angle value and the club faceorientation is established in the 3D scanning phase, thus in themeasurement phase, this rotational angle, together with the 3D position& orientation of the shaft, can be directly translated into the 3D faceangle, with the known 3D model of the club.

To increase the robustness of the system, instead of using a 1Dphase-shift pattern, a few phase shift patterns with different phasescan be stacked in a pre-defined sequence to form a 2D pattern, as shownfor example in FIG. 11. This arrangement will increase the robustness ofthe system as there is more information coded in the pattern; it alsohas the potential of increasing the measurement accuracy by averagingamong the multiple readings (for example, four in the illustrated case).

Alternatively, a phase shift pattern may be used that is modulated intwo dimensions as illustrated in the FIG. 12. By use the phase shiftmethod in two dimensions, it is possible to detect a reference point,for example the center of the brightest spot, with very high accuracy inboth directions. With the original dimensions of the patterns and theoptics of the imaging system known, it is then possible to estimate boththe distance (via changes in the spaces between grids of such featurepoints) and 3D orientation (via the distortion pattern formed by thegrids) of the shaft, in addition to the rotation angle around the shaft(via phase shift in one dimension). This capability removes the need fora stereo camera system and enables a single camera solution for clubmeasurement. This approach can also be applied to other sports such asbaseball, where the bat's orientation and distance measurement arecritical.

This 3D grid pattern can be arranged/stacked in various ways to improverobustness and accuracy as illustrated in the FIG. 13.

As the golf ball is blocked by the club head when viewed from thesystem, the time of impact (the maximum compression time) can only beestimated from the ball movement. The ball is not moving before theimpact instance and its 3D position can be measured using the stereovision method very accurately. With the ball's 3D position measured whenit is first seen and the balls speed measured using following frames,the time of impact can be estimated with an accuracy of 0.1 ms levelbased on the fact that the ball moves at a constant speed after theimpact. This timing information is important for at least tworeasons: 1) the club parameters need to be reported exactly at this timepoint; 2) the impact position on the club face can be estimatedaccurately for purposes of face angle compensation.

FIG. 14 illustrates the estimation of impact instance based on themeasurement of initial position and moving trajectory of the golf ball(after the occlusion by the club head), for a real case. In this figure,time 0 is the capturing time of the first frame in which the golfball ismoving out of the occlusion of the club head. Based on ball speed, theimpact time is determined to have been −3.10 ms.

With this impact time estimated accurately, the related 3D position ofthe club head and ball at this instance can be calculated accurately.Using the 3D model, the face angle and impact position can be reportedaccurately. Unlike existing systems, this face angle already compensatesthe club face angle variation of wood and drivers.

The club face angle variation along the surface for wood and drivers,also known as the bulge and roll factor, is illustrated in FIG. 15. Theface angle orientation is dependent on the location of the club face. Inthe case of an 11 inch bulge radius, in the illustrated example, adistance of 1 Omm across the club face corresponds to a difference oftwo degrees of a line perpendicular to the club face. In existingsystems, this variation commonly leads to a error of the reported faceangle, as this information is not available and a flat surface isassumed. However, with the 3D model available in the present system andthe impact position accurately measured, this error is automaticallyremoved.

With the methods described, all the club related data can be measured asshown in Table 1. Together with the 3D model of the club head, thesimple model of the golf ball and ball parameters (measured, forexample, using methods similar to those described in U.S. Pat. No.9,171,211 B2), the 3D scene of the golf ball launch can be fullyreconstructed with high accuracy. As there are different types of golfballs, some parameters, such as the exact diameter, may be obtained fromthe ball measurement result.

TABLE 1 The club parameters definition and measurement method ClubParamters Measurment to be Measured Definition Method Club Head Thespeed the club head Stereo Vision on Speed is traveling immediately ClubHead prior to impact. (COG) + Radar Attack Angle The vertical directionof Stereo Vision on the club head's geometric Club Head (COG) centermovement at maximum compression of the golf ball Club Path Club Path isthe direction Stereo Vision on the club head is moving Club Head (rightor left) at impact. (COG) Impact Position The contact position of theSweep path + on Club Face ball on the club face at impact instanceimpact estimation + 3D registration Club Face The direction the clubImpact position + Angle face is pointed at impact 3D model (left orright) Dynamic Lie The angle between the Stereo vision + at Impactcenter of the shaft and 3D registration the sole of the club

This 3D reconstruction can be realized with 3D tools like OpenGL, withinput of the 3D model of the club head, the ball and the measuredparameters about the movement of the head and the ball. The purpose isto allow the player examine the movement of the club and ball intheoretically infinite fine details in both space and time to understandthe relationship between the final delivery performance and the controlon the club. In this way, the player can improve his/her performancemore effectively.

FIG. 16 is a block diagram illustrating 3D reconstruction of the fulllaunching scene in accordance with an exemplary embodiment. A 3D model1601 of the club head obtained from scanning, a 3D model 1603 of thegolf ball, and club and ball movement parameters 1605 measured by themeasuring device are input to a 3D simulation engine 1607. The 3D modelof the golf ball may be based on a ball diameter measured by themeasuring device 110. The 3D simulation engine produces simulationresults 1609, which may be viewed by the user on the viewing device 120.The UI of the viewing device provides for interactivity, wherebyinteractive control inputs 1611 are provided to the 3D simulation engine1607. New simulation results are then produced and displayedaccordingly.

Using a sticker and image processing as described above, therequirements of stereo camera systems may be removed. This changesimplifies the system and reduces the cost. The 3D information providedby the stereo system is lost. However, 3D measurement can still be done.First, 3D scanning can be realized with a single camera and thestructured lighting of a 2D pattern with the club head rotating a fullrevolution before the camera. In addition, the first camera observingthe club movement can deduce the distance and 3D orientation of theshaft and the orientation around the shaft based on the observed 2Dphase shift marker. For the second camera observing the golf ball, againthe distance information can be estimated from the observed golf ballsize, which has an inverse relationship with the distance from thecamera. A much simpler hardware design results, as shown in FIG. 17. Ascompared to the system of FIG. 2, the camera pairs 101A, 101B and 103A,103B are replaced by single cameras 1701 and 1703. In still otherembodiments, the functions of the cameras 1701 and 1703 may be performedby a single multi-function camera.

It will be appreciated by those skilled in the art that the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential character thereof The disclosed embodiments aretherefore intended in all respects to be illustrative and notrestrictive. The scope of the invention is indicated by the appendedclaims rather than the foregoing description, and all changes that comewithin the scope and range of equivalents thereof are intended to beembraced therein.

What is claimed is:
 1. A method comprising: performing scanning of agolf club to obtain scanning information; using at least one camerapositioned behind the golf ball and at least one lighting unit to obtaina series of images of the golf club and golf ball during swinging of thegolf club; using a control unit and a radar unit to control the at leastone camera and at least one lighting unit; and providing the scanninginformation and the images to a modeling unit, the modeling unit togenerate a model of the golf club based on the scanning information andthe images.
 2. The method of claim 1, wherein the golf club has at mostone sticker attached thereto, the sticker bearing at least one modulatedbrightness pattern, the at least one modulated brightness pattern beingvisible or invisible to human eyes.
 3. The method of claim 2, whereinthe at least one brightness pattern is modulated in two dimensions. 4.The method of claim 2, wherein the sticker bears multiple separatemodulated brightness patterns.
 5. The method of claim 2, wherein thesticker is placed on a shaft of the golf club.
 6. The method of claim 1,comprising using the modeling unit to obtain a model of a golf clubswing and impact with the golf ball.
 7. The method of claim 6, whereinthe model accurately models a 3D shape of a face of the golf club. 8.The method of claim 1, comprising displaying an interactive videorepresenting a golf club swing, and impact with the golf ball.
 9. Themethod of claim 1, comprising using a first plurality of cameraspositioned behind the golfer to obtain the series of images of the golfclub during swinging of the golf club.
 10. The method of claim 1,wherein the scanning information is 3D scanning information, comprisingusing a second plurality of cameras positioned behind the golfer and atleast one further lighting unit to perform 3D scanning of the golf clubto obtain the 3D scanning information.
 11. A comprising: at least onecamera positioned behind the golf ball and at least one lighting unit,the at least one camera being configured to: perform scanning of a golfclub to obtain scanning information; and obtain a series of images ofthe golf club and golf ball during swinging of the golf club; a controlunit and a radar unit coupled to the at least one camera and the atleast one lighting unit to control the at least one camera and at leastone lighting unit; and a modeling unit connected to receive the scanninginformation and the images, the modeling unit to generate a model of thegolf club based on the scanning information and the images.
 12. Thesystem of claim 11, wherein the golf club has at most one stickerattached thereto, the sticker bearing at least one modulated brightnesspattern.
 13. The system of claim 12, wherein the at least one brightnesspattern is modulated in two dimensions.
 14. The system of claim 12,wherein the sticker bears multiple separate modulated brightnesspatterns.
 15. The system of claim 12, wherein the sticker is placed on ashaft of the golf club.
 16. The system of claim 11, wherein the modelingunit is configured to obtain a model of a golf club swing and impactwith the golf ball.
 17. The system of claim 16, wherein the modelaccurately models a 3D shape of a face of the golf club.
 18. The systemof claim 11, comprising a display coupled to the control unit fordisplaying an interactive video representing a golf club swing andimpact with golf ball.
 19. The system of claim 11, comprising a firstplurality of cameras positioned behind the golfer to obtain the seriesof images of the golf club during swinging of the golf club.
 20. Themethod of claim 1, wherein the scanning information is 3D scanninginformation, comprising a second plurality of cameras positioned behindthe golfer to perform 3D scanning of the golf club to obtain the 3Dscanning information.
 21. A method comprising: using at least one camerapositioned behind the golf ball to perform scanning of a golf club toobtain scanning information; using at least one other camera positionedbehind the golf ball and at least one lighting unit to obtain a seriesof images of the golf club and golf ball during swinging of the golfclub; using a control unit to control both the at least one camera andthe at least one other camera and the at least one lighting unit; andproviding the scanning information and the images to a modeling unit,the modeling unit to generate a model of the golf club based on thescanning information and the images.
 22. The method of claim 21, whereinthe golf club has at most one sticker attached thereto, the stickerbearing at least one modulated brightness pattern.
 23. The method ofclaim 22, wherein the at least one brightness pattern is modulated intwo dimensions.
 24. The method of claim 22, wherein the sticker bearsmultiple separate modulated brightness patterns.
 25. The method of claim22, wherein the sticker is placed on a shaft of the golf club.
 26. Themethod of claim 21, comprising: using the control unit and a radar unitto control the at least one camera and the at least one other camera.27. The method of claim 21, comprising using the modeling unit to obtaina model of a golf club swing and impact with the golf ball.
 28. Themethod of claim 21, wherein the model accurately models a 3D shape of aface of the golf club.
 29. The method of claim 21, comprising displayingan interactive video representing a golf club swing and impact with thegolf ball.
 30. A method comprising: capturing images of a sticker thatis attached to a piece of sports equipment using a single camera duringdynamic movement of the piece of sports equipment by a user, the stickerbearing at least one modulated brightness pattern, modulated in twodimensions; and processing the images to model dynamic movement of thepiece of sports equipment based on the images.